How does a moving head spot work ?

Application scenarios and types of moving head spots. Today I’m going to show you exactly how the Beam 350 works.


Moving head spots are usually used in stages and plazas. Professional Moving head spot is a high-tech product integrating electronics, machinery and optics. A qualified professional moving head spot must be stable and reliable, with excellent light efficiency, accurate positioning, good heat dissipation, and the light body and material structure must meet ergonomic requirements.

They can be divided into 250W, 575W, 1200W, 350W moving head Spot and other varieties from the power used. Among them, 1200W is the main lamp type for professional performance venues. This article focuses on the analysis of the structural principle of the beam 350. In a nutshell, the moving head spots is composed of three major systems: optical, mechanical, electrical and program control. The three systems are interrelated and organically combined to meet the needs of elements such as light, color, speed, direction, effect, heat dissipation, noise, and positioning.


1. Optical system

The most important consideration in optical system design is the utilization rate of light flux of the light source. Specific performance indicators include light intensity, uniformity, saturation, and spot size. There are two factors that affect the above indicators, one is the light source, and the other is the optical system structure and material selection. At present, domestic and foreign manufacturers and users basically recommend OSRAM or PHILIPS350W short-arc double-ended metal gas discharge lamps. Its characteristics are compactness, high brightness, high color temperature, good color rendering, and the light source can maintain a relatively stable color temperature in the process of dimming. The disadvantage is that the layering problem of the filler in the lamp tube, that is, the filler appears color banding in the arc imaging or condenses in the arc tube to form a shadow effect, which needs to be controlled to a minimum in the design of the optical structure. In the optical structure, in order to obtain a uniform mixed beam, a parabolic mirror can be used. To collect divergent or narrow beams, a mirror with scale processing or surface texture should be selected. Reflector systems made with specular reflective materials are better than refractive systems. When several beams need to be obtained from one light source, a prism or lens combination refractive system can be used. At present, the beam 350 moving heads all use the lens combination method, which is composed of aspherical (that is, parabolic) quartz lenses.The most important characteristic of a parabolic lens is to place a point light source at the focal point, which will result in a parallel beam. When designing the optical path, it is also necessary to consider the relationship between the light intensity distribution curve, the shape and the size of the light source, the aperture size of the reflective lens and the shape of the light source.


2. Mechanical system

Mechanical systems range widely, including materials, structures, mechanical properties, housing requirements, heat dissipation requirements, and more. The main considerations for the selection of lighting materials are: meeting the functional requirements of the lamp, manufacturing difficulty and economy. At present, the beam 350 mainly includes steel, plastic and aluminum alloy. Under the premise of satisfying the overall function of the lamp, the structural model of the lamp is designed, which is divided into different parts and uses different materials. For example, the 350W moving head beam pattern lamp, the lamp body shell is made of plastic parts, and the lamp body support frame, base, side plate and end plate are made of aluminum alloy castings, stamping parts, and car parts.

The beam 350 adopts a double-arm support structure, the light body rotates up to 540°horizontally and 255°vertically. The base part must be strengthened to meet the hanging and inverted requirements of the moving head light.

The mechanical properties of the lamp body are mainly reflected in the mechanical strength of the lamp body parts, so that the lamp body is not deformed, wear-resistant, corrosion-resistant, shock-resistant and pressure-resistant during continuous and effective working time; the lamp shell must have strict Waterproof, dustproof, antistatic and moisture proof requirements. According to the degree of dustproof and waterproof, the protection level requirements of different casings are divided: for example, the protection level of indoor computer lights is usually IP20, and the protection level of outdoor fixtures is usually IP44.

The mechanical structure of the 350W high-power moving head spot and the heat dissipation requirements are very important. If the heat dissipation system is defective, it will usually cause electrical parameter drift, color film, film breakage, plaques, and serious consequences such as crash, loss of step, and uncontrollability.


3. Electrical and program control part

A. Electrical characteristics and circuit design of moving head spots

The vast majority of professional 350W moving head spots around the world use rare gas discharge light sources. The starting and stable operation of the gas discharge bulb depends on the design of the circuit type, the selection of electrical components such as power supply and ballast. After the rare gas discharge bulb is started, it generally does not need a stabilization time. In order to ensure stabilization, the difference between the maintenance voltage of the circuit and the instantaneous voltage of the bulb should be sufficiently large during the entire AC cycle.

The starting, stability, extinguishing and restarting of the light source should be designed according to the characteristics of the light source. The starting voltage of rare gas discharge bubbles is very high, and it is required to use transformers, starting devices, semi-resonant circuits, etc. to increase the instantaneous starting voltage. The stability of the light source after starting depends on the matching of the ballast and circuit parameters. The basic function of the ballast is to prevent current runaway and keep the light source operating at its normal electrical characteristics. At present, manufacturers usually use two kinds of ballasts, one is an inductive rectifier and the other is an electronic rectifier. The advantage of the inductive rectifier is good stability, the disadvantage is that it is heavy, and it has higher requirements on the strength, handling, and loading and unloading of the lamp body; the electronic rectifier is essentially a power conversion circuit, which converts the input power supply current in terms of frequency, waveform and amplitude. Change. The advantages are light weight, convenient loading and unloading, and handling; the disadvantages are high structural design requirements and high maintenance costs.

The restart of the light source, in the conventional circuit design, due to the high temperature generated by the gas discharge bulb when working, causes the saturated gas in the bulb to form a vapor pressure resistance, and it is difficult to re-trigger the light source immediately. before a restart can be triggered. At present, international and domestic manufacturers basically adopt conventional circuit design.


B. Program control part

Nowadays,the moving head spots generally use DMX data format to write program files. The principle of DMX512: The speed of DMX data stream is 250K, that is, each BIT is a standard 4 microseconds. The data format of DMX is divided into the following parts: 1) IDLE (idle) or NODMXsituation (situation): when there is no DMX data packet output, it will be a high level signal; 2) BREAK: the beginning of a DMX data packet is an 88 Microsecond low output predictor {head}; 3) MARKAFTERBREAK (MAB): MAB is an 8 microsecond high or 2 pulses after BREAK; 4) STARTCODE (SC) start code: SC is The channel data at the beginning of the data stream, which has the same format as the channel data, generally 11 pulses or 44 microseconds; 5) MARKTIMEBETWEENFRAMES (MTBF): MTBF can be 0-1 seconds, less than 1 second, starting from each channel There can be MTBF before the start bit, which is high level; 6) CHANNELDATA (CD): The logical format of the channel data frame after SC is 1-512 or less than 512; 7) MARKTIMEBETWEENPACKETS (MTBP): After the valid data is sent Send high.

The moving head spot light effect is produced through different modeling scenes, different color changes, different viewing angles, changes in horizontal and vertical light angles, and speed, stroboscopic speed, aperture size changes, and focal length changes. The work of all these attribute indicators is realized through the transmission of the stepping motor, and the control of the moving head spot is completed by defining and programming the electrical operating parameters of the stepping motor.

Post time: Oct-22-2022